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Advantest Corporation

Gunma University

Harmonic Suppression Technique of

Magnetic Field Coupling Type Wireless

Power Transmission System Using ATAC Circuit

Tomonori Yanagida, Kosuke Machida,

Koji Asami, Yuki Endo, Haruo Kobayashi

Nov.2

S31-2

2/21

Research Objectives

Objective

Magnetic field coupling type wireless power transmission system

⚫ Resonance frequency matching

⚫ Magnetic field harmonic suppression

Approach

ATAC & harmonic suppression switching pattern

ATAC: Automatic Tuning Assist Circuit

3/21

Outline

• Research Background

• ATAC Circuit

• Harmonic Suppression Pattern

• Simulation

• Conclusion

4/21

Outline

• Research Background

• ATAC Circuit

• Harmonic Suppression Pattern

• Simulation

• Conclusion

5/21

Wireless Power Transmission

Electromagnetic

induction

Magnetic field

coupling

Electric field

resonance

Radio

wavelaser

Transmission

medium

Magnetic

field

Magnetic

field

Electric

field

Micro

waveLight

distance 2-3 [cm] 2-3 [m] 2-3 [mm] 2-3 [m]～ 2-3 [m]～

Degree

freedomFixed 3 dimensions plane 3 dimensions 3 dimensions

Distance

freedomimpossible possible possible possible possible

efficiency ～90% ～90% ～90% ～40% ～30%

Electric car & mobile electronics etc….

Wireless power transmission

Magnetic field coupling has good potential

Method & Characteristics

6/21

Magnetic Field Coupling Problem

●High Q value, and L & C with low resistance

●High precision resonance frequency adjustment

• Power supply & transmitter, transceiver

●Class D amplifier configuration

harmonic distortion generation

Automatic adjustment of resonance frequency

Magnetic field harmonics suppression system

Proposed Method

Problem

7/21

Outline

• Research Background

• ATAC Circuit

• Harmonic Suppression Pattern

• Simulation

• Conclusion

8/21

Equivalent Circuit of Magnetic Field Coupling

𝑸𝑻𝑿 =𝝎𝒐𝑳𝑻𝑿𝑹𝑻𝑿

, 𝑸𝑹𝑿 =𝝎𝒐𝑳𝑹𝑿𝑹𝑹𝑿

𝝎𝒐 =𝟏

𝑳𝑻𝑿𝑪𝑻𝑿=

𝟏

𝑳𝑹𝑿𝑪𝑹𝑿

𝜂 =1

1𝜅2𝑸𝑻𝑿𝑸𝑹𝑿

𝑹𝑳𝑹𝑹𝑿

+ 𝟏 + 𝟏 1 +𝑹𝑹𝑿𝑹𝑳

Power supply efficiency

9/21

Proposed Circuit: ATAC

ATAC (Automatic Tuning Assist Circuit)

Automatic correction of phase shift

between current & voltage

Main power supply & ATAC section

shift switching phase by 90°

10/21

ATAC Principle

Add together

Main power supply

Auxiliary power supply having phase 90°

11/21

Conventional Circuit

Slope 𝑪𝑻𝑿 Output current

Error of resonance frequency 0.80%~3.78%

Error of output current 60%～80%

126pF 124pF 122pF 120pF 117pF

12/21

ATAC Circuit

Output current

Error of resonance frequency 0.80%~3.78%

Error of output current 0%～20%

123pF 122pF 121pF 120pF 117pF

13/21

Outline

• Research Background

• ATAC Circuit

• Harmonic Suppression Pattern

• Simulation

• Conclusion

14/21

Harmonic Suppression Switching Pattern

2018/11/7

𝒇 𝒕 =

𝐤=𝟏

∞𝟏

𝒌𝝅𝐬𝐢𝐧 𝟐𝒌𝒇𝝅𝒕 (𝐤 = 𝟏, 𝟑, 𝟓,⋯ )

1

0 1/2f 1/f ｆ 3ｆ 5ｆ 7ｆ

Fourier transformation

ｔ

ｆ

Time Frequency

Harmonic suppression Algorithm

Duty50%

Switching output pattern

HD : Harmonic Distortion

15/21

Harmonic Suppression Switching Pattern

2018/11/7

f t − f t − τ − f t + τ

=

k=1

∞1

𝑘𝜋1 − 2cos 2𝑘𝑓𝑖𝑛𝜋𝜏 sin 2𝑘𝑓𝑖𝑛𝜋𝑡

In case HD3 suppression 𝒇𝒊𝒏𝝉 =𝟏

𝟏𝟖

Time waveform Spectrum

Specific frequency suppression switching pattern

16/21

Outline

• Research Background

• ATAC Circuit

• Harmonic Distortion pattern

• Simulation

• Conclusion

17/21

Apply HD3 Suppression Pattern

SW1

SW3 ９０°phase difference

・Harmonics suppression

・Operation of ATAC not Duty50%

Objective

18/21

Spectrum of Inductor Current

Duty 50% switching

HD3 suppression switching

-20dB suppression

19/21

Output Current of HD3 Suppression

Output current

Error of resonance frequency 0.80%~3.78%

Error of output current 0%～20%

123pF 122pF 121pF 120pF 117pF

20/21

Outline

• Research Background

• ATAC Circuit

• Harmonic Distortion pattern

• Simulation

• Conclusion

21/21

Conclusion

2018/11/7

⚫Wireless power supply system

Automatically adjust resonance frequency

⚫ATAC circuit can operate

without duty 50% switching.

⚫Harmonic suppression pattern switching

HD3 suppression